1. Field of the Invention
The present invention relates to an isocyanurate derivative obtainable by a reaction of tris-(2,3-epoxypropyl) isocyanurate with a carboxyl group-containing compound, which is excellent in heat resistance. This isocyanurate derivative is a highly viscous liquid which has heat resistance attributable to a triazine ring and water-solubility attributable to hydroxyl groups and which contains little ionic chlorine, and it is useful as e.g. a thickening agent in an electric or electrical field for e.g. a flux composition.
2. Discussion of Background
As a catalyst for a reaction of an epoxy compound such as tris-(2,3-epoxypropyl) isocyanurate, with a carboxyl group-containing compound, a tertiary amine or a quaternary ammonium salt is commonly used, but such a catalyst is likely to often bring about a ring-opening polymerization reaction of epoxy groups as a side reaction to form an insoluble substance. JP-A-2-275867 discloses a reaction product of tris-(2,3-epoxypropyl) isocyanurate with a carboxyl group-containing compound, and a process for its production. However, if a quaternary ammonium salt is used as the catalyst disclosed in the Examples, or if the reaction is carried out at a high temperature in the absence of a catalyst, a part of tris-(2,3-epoxypropyl) isocyanurate undergoes ring-opening polymerization to form an insoluble substance as a by-product. Since the product is highly viscous liquid, there has been a problem that it has to be diluted with a solvent or heated to a high temperature to reduce the viscosity and remove the insoluble substance by filtration while it is still hot. Further, if a quaternary ammonium chloride is used, and if it remains in the product, it may adversely affect the electrical properties, since it is a substance having ionic chlorine.
Further, epichlorohydrin is used as a starting material in the process for producing tris-(2,3-epoxypropyl) isocyanurate, and if an ethylene chlorohydrin moiety as an epoxy precursor is present, such a moiety will remain in the molecule as hydrolyzable chlorine. This hydrolyzable chlorine does not usually change to ionic chlorine hazardous to the field of electronic and electric materials, even when treated at a high temperature for a long time. This may be explained in such a way that even if dehydrochlorination takes place to form ionic chlorine, such ionic chlorine will immediately undergo an addition reaction with an epoxy group present in the vicinity to again become to be an ethylene chlorohydrin moiety. Accordingly, usual tris-(2,3-epoxypropyl) isocyanurate contains no ionic chlorine.
However, when a reaction product of tris-(2,3-epoxypropyl) isocyanurate with a carboxyl group-containing compound is produced, formation of ionic chlorine has been observed surprisingly.
Namely, it has been difficult to obtain a reaction product of tris-(2,3-epoxypropyl) isocyanurate with a carboxyl group-containing compound, which contains little ionic chlorine and is free from an insoluble substance, by the conventional technology.